Steven M. Lev

Chemical fractionation of Cu and Zn in stormwater, roadway dust and stormwater pond sediments

This study evaluated the chemical fractionation of Cu and Zn from source to deposition in a stormwater system. Cu and Zn concentrations and chemical fractionation were determined for roadway dust, roadway runoff and pond sediments. Stormwater Cu and Zn concentrations were used to generate cumulative frequency distributions to characterize potential exposure to pond-dwelling organisms. Dissolved stormwater Zn exceeded USEPA acute and chronic water quality criteria in approximately 20% of storm samples and 20% of the storm duration sampled. Dissolved Cu exceeded the previously published chronic criterion in 75% of storm samples and duration and exceeded the acute criterion in 45% of samples and duration. The majority of sediment Cu (92-98%) occurred in the most recalcitrant phase, suggesting low bioavailability; Zn was substantially more available (39-62% recalcitrant). Most sediment concentrations for Cu and Zn exceeded published threshold effect concentrations and Zn often exceeded probable effect concentrations in surface sediments.

Watershed-scale analysis of pollutant distributions in stormwater management ponds

Stormwater management ponds have become a common Best Management Practice in urban and suburban landscapes. Stormwater management ponds are designed to hold runoff from impervious surfaces and allow the settling of sediments and associated pollutants. Various semi-aquatic and aquatic wildlife species have been documented using stormwater management ponds as habitat, but these wetland-like systems are not managed to adhere to freshwater habitat pollutant guidelines. To address the potential for pollutant exposure for wildlife, we used a random sample of 68 stormwater ponds and estimated the proportion of ponds in a third-order watershed that exceed toxicity guidelines for trace metals and polycyclic aromatic hydrocarbons in sediments and chloride in surface waters. Ninety-six percent of ponds exceeded consensus-based threshold effect concentrations for at least one trace metal. Concentrations of at least one of the PAHs measured exceeded the threshold effects concentration in 63% of the ponds. Nine percent of ponds exceeded chronic toxicity levels of chloride on all sampling dates, and 21% exceeded acute toxicity concentrations on at least one sampling date. More studies are needed to evaluate toxic effects of pollutants in stormwater management ponds and the potential for interactive effects of pollutants on wildlife.

Impacts of weathered tire debris on the development of Rana sylvatica larvae

Highway runoff has the potential to negatively impact receiving systems including stormwater retention ponds where highway particulate matter can accumulate following runoff events. Tire wear particles, which contain about 1% Zn by mass, make up approximately one-third of the vehicle derived particulates in highway runoff and therefore may serve as a stressor to organisms utilizing retention ponds as habitat. In this study, we focused on the potential contribution of tire debris to Zn accumulation by Rana sylvatica larvae and possible lethal or sublethal impacts resulting from exposure to weathered tire debris during development. Eggs and larvae were exposed to aged sediments (containing either ZnCl2 or tire particulate matter, both providing nominal concentrations of 1000 mg Zn kg(-1)) through metamorphosis. Water column Zn was elevated in both the ZnCl2 and tire treatments relative to the control treatment, indicating that aging allowed Zn leaching from tire debris to occur. Tissue Zn was also elevated for the ZnCl2 and tire treatments indicating that Zn in the treatments was available for uptake by the amphibians. Exposure to both ZnCl2 and tire treatments increased the time for larvae to complete metamorphosis in comparison with controls. We also observed that the longer the organisms took to complete metamorphosis, the smaller their mass at metamorphosis. Our results indicate that Zn leached from aged tire debris is bioavailable to developing R. sylvatica larvae and that exposure to tire debris amended sediments can result in measurable physiological outcomes to wood frogs that may influence population dynamics.

Stormwater ponds as a source of long-term surface and ground water salinisation

We investigated the spatial and temporal distribution of chloride and conductivity in a long hydroperiod retention pond and two short hydroperiod detention ponds. In both cases we observed greatly elevated conductivities in surface and ground waters with peak conductivities exceeding 45 mS cm−1 in the retention pond and 25 mS cm−1 in one detention pond. Pond ground water conductivity remained highly elevated into the summer months and never declined to local stream conductivity levels. Conductivity and chloride concentrations were also elevated in floodplains adjacent to all ponds throughout the year. First order streams draining the detention pond floodplain were consistently elevated in conductivity and were a year-round net source of ions to the second order stream into which they flowed. These results indicate that both short and long hydroperiod stormwater ponds have the potential to serve as long-term, year round sources of chloride to adjacent surface and ground waters.

Vegetation dynamics and mesophication in response to conifer encroachment within an ultramafic system

The biological, ecological, and evolutionary significance of serpentine habitats has long been recognised. We used an integrated physiochemical dataset combining plot spatial data with temporal data from tree cores to evaluate changes in soils and vegetation. Data suggest that this unique habitat is undergoing a transition, endangering local biodiversity and endemic plant species. The objective of this work was to analyse the vegetation dynamics of a xeric serpentine savanna located in the Mid-Atlantic, USA. We employed vegetation surveys of 32 10 � 15m quadrats to obtain woodyspeciescomposition,density,basalarea,anddevelopedaspatialphysiochemicaldatasetofsubstrategeochemistryto independently summarise the data using regression and ordination techniques. This information was interpreted alongside historical, dendrochronologic and soil stable carbon isotopic data to evaluate successional dynamics. Comparisons among geologic, pedologic and vegetation environmental drivers indicated broad correlations across an environmental gradient, correspondingtoagrasslandtoforesttransition.Thewoodlandcommunitiesappeartobepartofacomplexsoilmoistureand chemistry gradient that affects the extent, density, basal area and species composition of these communities. Over the gradient, there is an increase in a diversity, a decrease in the density of xeric and invasive species, and an increase in stem density of more mesic species. Dendrochronology suggests poor recruitment of xeric species and concomitant increase in more mesic species. The data indicated that former C4-dominated grasslands were initially invaded by conifers and are now experiencing mesophication, with growing dominance by Acer, Nyssa and more mesic Quercus and Fagus species. Additional keywords: edaphic, plant-soil relations, serpentine, succession.

Toxicological applications of cryogenic laser ablation inductively coupled plasma time of flight mass spectrometry (CLA-ICP-TOF-MS)

The analysis of acid digested bulk tissue samples by ICP-MS is a primary method for toxicologists when trying to characterize the uptake and storage of a trace metal by an organism. This approach is sensitive, reliable and reproducible but requires the homogenization of the tissue for analysis. This procedure does not provide any information on the distribution of the analyte of interest within the tissue sample. Sub-sampling is a possible alternative method for preserving distribution data but in many cases sub-sampling on the scale necessary for useful information is not an option due to sample size limitations. By coupling a laser ablation system equipped with a cryogenic cell to an Inductively Coupled Plasma Mass Spectrometer (CLA-ICP-MS), it is possible to achieve high-resolution trace metal distribution data on toxicological tissue samples. A cryo-cell is critical for proper ablation of soft tissue samples by LA-ICP-MS. The system used for the work presented is a commercially available cryo cell from GeoMed Analytical capable of temperatures as low as −30 °C, coupled to a GBC Scientific ICP-Time of Flight-MS (ICP-TOF-MS). The speed of the TOF system is an ideal platform for the analysis of the transient signal produced by laser ablation and has detection limits that are comparable to traditional ICP-MS (i.e. low ppb range). This system is suitable for the ablation of a range of tissues with a spatial resolution of 25 microns for most elements. Results will be presented that identify the optimal ablation settings for obtaining accurate and precise Zn and Cu isotope ratios in tissue samples. A demonstration of the potential toxicological application of the CLA-ICP-TOF-MS system using a Zn stable isotope tracer in the earthworm Lumbricus terrestris will also be presented.

Influence of Modern Stormwater Management Practices on Transport of Road Salt to Surface Waters

Application of road salts in regions with colder climates is leading to ground and surface water contamination. However, we know little about how modern stormwater management practices affect the movement of road salt through urban watersheds. We investigated groundwater contamination and transport of road salts at two stormwater ponds in Baltimore County, Maryland. In association with the ponds, we documented a plume of contaminated groundwater that resulted in Cl- loadings to the adjacent stream of 6574 to 40 008 kg Cl- per winter, depending on winter snowfall. We also monitored Na+ and Cl- ion concentrations and the temporal dynamics of conductivity at a range of stream sites in watersheds with and without stormwater management ponds. Streams draining watersheds with stormwater ponds had consistently higher conductivities and Cl- concentrations during base flow conditions and often exhibited greater peaks in Cl- and conductivity associated with winter storms and subsequent melting events, despite the degree of watershed development. Our results indicate that modern stormwater management practices are not protecting surface waters from road salt contamination and suggest they create contaminated plumes of groundwater that deliver Cl- and Na+ to streams throughout the year.

Application of Synchrotron Methods to Assess the Uptake of Roadway-Derived Zn by Earthworms in an Urban Soil

Abstract The impact of human activities on biogeochemical cycles in terrestrial environments is nowhere more apparent than in urban landscapes. Trace metals, collected on roadways and transported by storm water, may contaminate soils and sediments associated with storm water management systems. These systems will accumulate metals and associated sediments may reach toxic levels for terrestrial and aquatic organisms using the retention basins as habitat. The fate and bioavailability of these metals once deposited is poorly understood. Here we present results from a dose-response experiment that examines the application of synchrotron X-ray fluorescence methods (μ-SXRF) to test the hypothesis that earthworms will bio-accumulate Zn in a roadway-dust contaminated soil system providing a potential pathway for roadway contaminants into the terrestrial food web, and that the storage and distribution of Zn will change with the level of exposure reflecting the micronutrient status of Zn. Lumbricus friendi was exposed to Zn-bearing roadway dust amended to a field soil at six target concentrations ranging from background levels (45 mg/kg Zn) to highly contaminated levels (460 mg/kg Zn) designed to replicate the observed concentration range in storm-water retention basin soils. After a 30 day exposure, Zn storage in the intestine is positively correlated with dose and there is a change in the pattern of Zn storage within the intestine. This relationship is only clear when μ-SXRF Zn map data is coupled with a traditional toxicological approach, and suggests that the gut concentration in L. friendi is a better indicator of Zn bioaccumulation and storage than the total body burden.

Geologic and Edaphic Controls on a Serpentine Forest Community

Abstract This study examined woody vegetation, edaphic factors, bedrock geochemistry, petrography, and outcrop structure to evaluate some of the community-structuring factors in an ultramafic terrain of Maryland. Analyzing the dynamic nature of combined geological and ecological processes can detect correlative relationships between factors that are typically considered as independent such as tectonically driven bedrock fracturing and ecological community interaction. This study provides evidence for structural variation in fracture density of bedrock as a partial control on tree species distribution in an ultramafic woodland/forest ecosystem. Increases in the number of bedrock fractures correlates negatively with plot-level volumetric soil moisture. Additionally, the degree of serpentinization of the ultramafic parent material results in compositional variation in Ca, Mg, and Ni of parent materials and soils. The combination of these factors provides a significant level of control on the distribution of xeric tree species.

Attenuation of copper in runoff from copper roofing materials by two stormwater control measures.

Concerns have been raised over diffuse and non-point sources of metals including releases from copper (Cu) roofs during storm events. A picnic shelter with a partitioned Cu roof was constructed with two types of stormwater control measures (SCMs), bioretention planter boxes and biofiltration swales, to evaluate the ability of the SCMs to attenuate Cu in stormwater runoff from the roof. Cu was measured as it entered the SCMs from the roof as influent as well as after it left the SCMs as effluent. Samples from twenty-six storms were collected with flow-weighted composite sampling. Samples from seven storms were collected with discrete sampling. Total Cu in composite samples of the influent waters ranged from 306 to 2863 μg L(-1) and had a median concentration of 1087 μg L(-1). Total Cu in the effluent from the planter boxes ranged from 28 to 141 μg L(-1), with a median of 66 μg L(-1). Total Cu in effluent from the swales ranged from 7 to 51 μg L(-1) with a median of 28 μg L(-1). Attenuation in the planter boxes ranged from 85 to 99% with a median of 94% by concentration and in the swales ranged from 93 to 99% with a median of 99%. As the roof aged, discrete storm events showed a pronounced first-flush effect of Cu in SCM influent but this was less pronounced in the planter outlets. Stormwater retention time in the media varied with antecedent conditions, stormwater intensity and volume with median values from 6.6 to 73.5 min. Based on local conditions, a previously-published Cu weathering model gave a predicted Cu runoff rate of 2.02 g m(-2) yr(-1). The measured rate based on stormwater sampling was 2.16 g m(-2) yr(-1). Overall, both SCMs were highly successful at retaining and preventing offsite transport of Cu from Cu roof runoff.